I think what @IWDstudios said is about customizing. He has his point. Because when a user customizing the PSD . Just imagine they are editing some elements on the PSD and straight away export the selected sliced. That save a lot of time compare to this technique.
While this technique can be useful for a web designer to convert PSD to HTML for a project.
Either old way or new way, there is always a reason why people using it. Cheers!
Thanks for the tip Chris, nice one.
You forgot to mention that hitting the opt+click once again will undo the “hide other visible” action.